<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="js/jquery-3.3.1.min.js"></script>
    <script>
        $(function(){
            // DOM对象 -----> jQuery对象
            var objDom = document.getElementById('d1')
            $(objDom).css('color', 'red')


            // jQuery对象 -----> DOM对象
            var objJquery = $('#p1')
            // objJquery[0].style.color = 'blue'
            objJquery.get(0).style.color = 'blue'
        })
    </script>
</head>
<body>
    <div id="d1">hello</div>
    <p id="p1">world</p>
</body>
</html>